一、引言日本从1977年1月起已采用约瑟夫森结电压标准代替原来的标准电池组作为国家基准。约瑟夫森结产生的电压仅由物理常数与外加在结上的微波频率确定。按此原理,电压精度可用频率精度确定。但是在约瑟夫森结上产生的恒定电压至多是几个 mV,故采用通过电 I. Introduction Japan has adopted the Josephson junction voltage standard instead of the original standard battery pack as a national benchmark since January 1977. The voltage generated by the Josephson junction is only determined by the physical constant and the frequency of the microwave applied to the junction. According to this principle, the voltage accuracy can be determined by the frequency accuracy. However, the constant voltage generated on the Josephson junction is at most a few mV, so the adoption of electricity